155 - Country-wide scope of pyrethroid resistance in Aedes aegypti in Peru and implications for resistance management

Aedes aegypti reinvaded Peru in 1984, with initial detection in Amazonian states near Brazil and recent establishment in southern states near Chile. More than 144,000 cases of dengue have been reported in 2017-2020.  Collaborative vector surveillance work with local Ministry of Health and Military units allowed collection of 2,400 Ae. aegypti from 55 locations in coastal and jungle states from 2017 to 2022. Specimens were tested for knockdown resistance (kdr) mutations V1016I and F1534C.  Mosquitoes from northern coastal and four northern jungle states were fixed or nearly fixed (≥ 95%) for 1534CC; 1534FF mosquitoes (29-100%) were found in southern and one northern jungle states.  Moderate to high levels of 1016II were found in northern coastal states (20-86%); low to high levels of 1016II were found in northern jungle states (0-89%); and low to moderate levels of 1016II were found in southern states (0-24%). Eight genotypes were observed (IICC, IIFC, VICC, VIFC, VIFF, VVCC, VVFC, VVFF) with resistant genotypes (VICC, IICC) indicative of higher resistance (20X-60X), recorded in northern states, and less resistant genotypes (VVCC, VVFC, VVFF) indicative of lower resistance (4X) in southern states. Our results showed that kdr mutations are broadly distributed in Peruvian Ae. aegypti, yet with considerable variation even within close geographic proximity.  A higher proportion of more resistant genotypes were found in northern states, which have been subject to many years of control efforts, than in southern regions, more recently colonized locations or locations with little vector control activity. This may explain decreased effectiveness of pyrethroid insecticides for Ae. aegypti control in northern Peru. Phenotypic and biochemical responses of northern jungle Ae. aegypti to pyrethroids will further validate the use of these genetic markers as a rapid insecticide resistance screening tool.  This study provides insights into pyrethroid resistance mechanisms and may guide mosquito control operations.